This invention relates to a method of producing surfactants from lignin. More particularly, the invention discloses a process of alkylating and oxidizing lignin to form a group of compounds having surfactant properties. These compounds may be used in surfactant flooding to recover hydrocarbons from underground formations. Alkyloxybenzoic acids which may be found in the lignin reaction products of this invention may also be used in surfactant flooding.
Surface active compounds or surfactants have become extremely important chemicals in our society. Numberless types of surfactants are used for a myriad of applications. To work effectively, most surfactants require water soluble and oil soluble characteristics. It is these mixed characteristics which enable surfactants to lower the surface tension between two disparate liquids.
One problem with many surfactants is their high cost of manufacture. Surfactants which are relatively cheap have an inherent advantage in the market place.
A minor use of surfactants has been in surfactant flooding systems for enhanced oil recovery. But because of the relatively high cost of surfactants, surfactant flooding systems for oil recovery have generally not been economical.
Surfactant flooding to recover oil has been actively investigated due to the relatively poor ability of water floods to displace remaining oil from a reservoir's pore stucture. Because of the structure of the reservoir and surface tensions involved, the flood water may form channels or fingers, bypassing the oil in the formation.
Investigations of ways to increase oil recovery by improving the displacement ability of water floods have produced useful surfactants which reduce the interfacial tension between oil and water in the reservoir. With lower interfacial tensions, oil that is trapped in the pore structure can be dispersed into the water as smaller and more easily deformable droplets. Many types of surfactants have been investigated and the choice of which surfactant to employ in a water flood operation is dependent upon reservoir characteristics as well as the cost and availability of the surfactants.
Lignin is a waste by-product that the pulping industry produces in prodigious amounts. As a result, a large research effort has been undertaken over the last 40 years in attempts to find uses for the large volume of lignin by-product.
Lignin is comprised of polymeric chains having molecular weights over 10,000 with multiple different units. One substantial monomeric unit contained in the lignin polymeric chains is propane phenol.
Numerous oxidation methods of lignin have been tried. The oxidation of lignin by potassium permanganate and sodium periodate is disclosed in Griggs, B. F., "Modification of Kraft Lignins by Sulfomethylation and Oxidative Sulfonation: Structure and Mechanisms", Ph.D. Dissertation, North Carolina State University (1985). The Griggs Dissertation isolated eight specific benzoic acid structures having single or double aromatic rings as oxidation products of lignin. Other potential oxidizing agents have been used to oxidize side chains on benzene. Potassium permanganate is disclosed in Whitmore, F. C. and Woodward, G. E., Organic Synthesis, Coll., Vol. 1, p. 159 (1944). Chromic acid in aqueous solution is disclosed in Pacaud, R. A. and Allen, C. F. H., Organic Synthesis, Coll., Vol. 2, p. 336 (1943). Chromic acid in acetic acid as an oxidizing agent of side chains has been disclosed in Rieveschl, G., Jr., and Ray, F. E., Organic Synthesis, Coll., Vol. 3, p. 420 (1955). Aqueous sodium dichromate is another potential oxidizer of lignin side chains at elevated temperatures. See, Friedman, L. J. Organic Chemistry, Vol. 43, p. 80 (1963). Nitric acid has also been employed to oxidize lignins as disclosed in Popa, V. I., Cellulose Chem. Technology, Vol. 19, p. 657-661 (1985).
Mild oxidizing agents of lignin such as copper(II) oxide or sulfate, cobalt(II) oxide or sulfate and nitrobenzene are disclosed in Sarkanen, K. V. and Ludwig, C. H., "Oxidation", Chapter 11 of Lignins--Occurrence, Formation, Structure, and Reactions, John Wiley & Sons, Inc. (1971); and Leopold, B., "Aromatic Keto- and Hydroxy-Polyethers as Lignin Models", Acta Chemica Scandinavica, Vol. 4, p. 1523-37 (1950).
Several literature references have discussed a procedure for identifying various structures within lignin polymers. This identification method involves methylating lignin at phenolic groups followed by oxidation with potassium permanganate or potassium permanganate followed by hydrogen peroxide. Please see, Freudenberg, K. and Chen, C. L., Chem. Ber., Vol. 93, p. 2533 (1963); Freudenberg, K., Chen, C. L. and Cardinale, G., Chem. Ber., Vol. 95(11), p. 2814 (1962); and Griggs, B. F., Ph.D. Dissertation previously cited.
Procedures on how to make alkyl ethers from lignins may be found in Brauns, F. E., Lewis, H. F. and Brookbank, E. B., "Lignin Ethers and Esters", Industrial and Engineering Chemistry, Vol. 37(1) (1945); and Jones, G. M. and Brauns, F. E., "Ethers of Certain Lignin Derivatives", J. Paper Trade, Vol. 119(11), p. 108 (1944).
The patent literature discloses multiple uses for various oxybenzoic acid compounds. These uses include adhesives, thermoplastic elastomers, structural molding foam, heat sensitive recording paper, photosensitive uses, a bleach composition, antiseptic, flame retardant compounds, and liquid crystal uses. Aldrich Laboratories and Frinton Laboratories, Inc. both sell substantially pure alkyloxybenzoic acids having various alkyl chains lengths. However, none of the disclosed uses of oxybenzoic acids relate to enhanced oil recovery.
Several publications have disclosed the use of alkylcarboxylate surfactants and alkylbenzoic acid surfactants in enhanced oil recovery. But these disclosures do not mention alkyloxybenzoic compounds. Disclosures and literature on carboxylates include U.S. Pat. Nos. 4,556,495; 4,561,501; as well as Shaw, J. E., "Enhanced Recovery Using Carboxylate Surfactant Systems", J. of American Oil Chemists Society, Vol. 61(8), p. 1389 (August 1984); and Shaw, J. E., "Carboxylate Surfactant Systems Exhibiting Phase Behavior Suitable For Enhanced Oil Recovery", J. of American Oil Chemists Society, Vol. 61(8), p. 1395 (August 1984).